Portable printing devices are well known in the art. Japanese Patent application Publication No. 2015-160427 describes an example of one such printing device provided with a belt clip. By attaching the printing device to a waist belt with this belt clip, the user can use the printing device portably. To this printing device, a structure disclosed in Japanese Patent application Publication No. 2015-208920 may be applicable. The printing device described in Japanese Patent application Publication No. 2015-208920 includes a rear cover rotatably supported to be opened and closed. The rear cover is provided with support cylinders (corresponding to bearings) that rotatably support both ends of a rotational shaft of a platen roller. The support cylinders may be presumably fitted with a holder, and the holder may be fixed to the rear cover with screws.